The present invention relates in general to the field of micro electro mechanical systems (MEMS) for medical or non-medical use. More particularly, the invention relates to an active slender (small diameter) tube or tubular object or instrument that can be incorporated into a complex machine system or a pipe line to perform a machine inspection or system maintenance, or can be used as a medical micro electro mechanical systems such as an active catheter or an active guide wire as incorporated into a human blood vessel or organ for utilization in performing a diagnosis or medical treatment.
Such slender tubes or tubular objects as combined or assembled are also applicable to building an articulated or multi-articular, or multi-leg robot, or an elaborate toy.
In recent years there have been increasingly used endoscopes with driving wires for diagnosis of, e. g., the large intestine. And efforts have also been exerted in developing active catheters in which a shape memory alloy (hereinafter also referred to SMA) that is deformable when electrically heated is utilized to make up an actuator.
Further, with the progress of micro-machining technologies, efforts have been made to develop varieties of micro-sensors and active micromechanisms that may effectively be incorporated into catheters for medical applications.
For example, Japanese patent application No. H10-11258 filed Jan. 23, 1998 by the inventor of this application (JP Laid-Open publication No. H11-48171 published Feb. 23, 1999) proposes an active catheter of an outer skeleton type in which a liner coil is disposed outside of a plurality of, e.g., three, actuators which are made of a shape memory alloy. The SMA made actuators are electrically energized to permit the active catheter to be bent or flexed.
As to an extending and retracting mechanism for active catheters, there has been proposed an intra-tubular traveling apparatus having a tubular diameter of around 1 cm utilizing the inflation and contraction of a balloon under an atmospheric pressure, with which have been made on an experimental basis an endoscope guidance system for large intestines and a pipe orifice inspection guidance systems for town gas conduits (see xe2x80x9cThe World of Micro-mechanismsxe2x80x9d by T. Hayashi et al, Journal of the Japan Society of Acoustics, Vol. 49, No. 8, 1993).
An extending and retracting mechanism having a number of balloons disposed on its side surfaces has also been proposed. This is designed to permit the catheter to be advanced in a blood vessel as the inflation of the balloons pushes them against the inner wall of the blood vessel and their contraction and expansion in its axial direction are repeated (see xe2x80x9cPotential of Microsystems in medicinexe2x80x9d, Minimally Invasive Therapy and Applied Technology, 4: 267-275, 1995, A. E. Guver et al).
Active slender tubes so far proposed, such as those catheters or the like described above have not yet been sufficient, however, in their bendability and extendibility achievable, nor have they been wide enough in their degrees of freedom of movement selectable. Furthermore, if a single catheter is sought to have many more functions, its limited diameter and the need for a sufficiently spacious working channel in it have restricted the number of wires that could be incorporated to an insufficient extent.
It should also be noted that in orienting a manually operated catheter or guide wire that is normally bent towards its distal end in the form of the letter xe2x80x9cJxe2x80x9d so as to allow it to enter, e. g., into one of two blood vessels at their junction, it has been common practice to attempt to rotate the catheter or guide wire at its proximal end or side in order to rotate it at that distal end. Then, if the catheter or guide wire has in its midway a loop or an intricate travel or span, the torque to act to transmit the rotation at the proximal end to the distal end may fail to be well transmitted through the body of the catheter or guide wire, resulting in an insufficient manner, thus an inaccurate rotation of the catheter or guide wire at the distal or its foremost end will occur. This may be called a poor torquability.
Further, when the catheter or guide wire is pushed at its proximal end in order to advance its distal end towards a target position in a blood vessel, if the catheter or guide wire has a loop or an intricate travel or span a deflection that would then occur in the body of the catheter or guide wire would tend to prevent the pushing force applied at the proximal end from being accurately transmitted to the distal end, thus resulting in an imprecise positioning of the catheter or guide wire at its foremost end. This may be called poor pushability.
On the other hand, positioning the catheter or guide wire by retraction can be achieved relatively accurately. However, this operation requires the catheter or guide wire to be first advanced beyond the target position. Stiffening the catheter or guide wire improves its pushability and torquability, but increases the risk of perforation. Conversely, if the stiffness is reduced too much, deflection would prevent the catheter or guide wire from advancing any further however hard it may be pushed.
With the foregoing disadvantages or inconveniences of the prior art borne in mind, it is accordingly an object of the present invention to provide an improved active slender (small diameter) tube or tubular object or instrument that can be embodied as an active catheter, guide wire or any other micro electro mechanical systems or a system""s active micro-component as previously described.
It is also an object of the present invention to provide such a slender (small diameter) tube or tubular object or instrument that is simple in construction and has an expanded capability of movement, i.e., torsionally rotating, bending, extending and/or and retracting an active portion thereof, i.e., a portion thereof that is required to act, and/or adjusting stiffness of such a portion, to a required extent or extents with ease and precision.
It is also an object of the present invention to provide such a slender (small diameter) tube or tubular object or instrument of the outer skeleton type that meets the requirements described above.
Another object of the present invention is to provide an improved method of making such a slender (small diameter) tube or tubular object or instrument of the outer skeleton (exoskeletal) type that permits manufacture thereof with increased precision.
These and other objects which will become more readily apparent hereinafter are attained in accordance with the present invention.
According to the principles of the present invention in a first aspect thereof and in a certain form of implementation thereof, there is provided an active slender tube that is provided with a torsionally rotating mechanism. In specific terms, this form of implementation of the invention provides an active slender (small diameter) tube or tubular object or instrument that has a torsionally rotating mechanism mounted on or in the body portion thereof for torsionally rotating an active portion of the slender tube or tubular object or instrument as it is embodied, i.e., as an active catheter or guide wire or any other micro electro mechanical system or a system""s active micro-component.
According to an alternative form of implementation of the principles of the present invention, there is provided an active slender tube that is provided with an extending and a retracting mechanism. In specific terms, the slender (small diameter) tube or tubular object or instrument has an extending and retracting mechanism mounting on or in the body portion thereof for extending and retracting an active portion of the slender tube or tubular object or instrument as it is embodied, i.e., as an active catheter or guide wire, or any other micro electro mechanical system or system""s active micro-component. The extending and retracting mechanism here comprises an elastically deformable outer skeleton that may include an outer elastically deformable tube or tubular member or element, and an extending and retracting actuator disposed inside the outer skeleton and secured or fastened thereto. The extending and retracting member is made of a shape memory alloy (SMA) and upon deformation to have a length varied from the length of the SMA made actuator in its natural shape memory state is secured or fastened to the elastically deformable outer skeleton.
According to a further alternative form of implementation of the principles of the present invention, there is provided an active slender tube that is provided with a stiffness control mechanism. In specific terms, this form of implementation of the principles of the present invention provides active slender (small diameter) tube or tubular object or instrument that has a stiffness control mechanism mounted on or in the body portion thereof for controlling stiffness of an active portion, or the body portion, of the slender tube or tubular object or instrument towards its forward end thereof as it is embodied, i.e., as an active catheter or guide wire, or any other micro electro mechanical system or a system""s active micro-component.
According to a specific form of implementation of the principles of the present invention, there is provided an active slender tube as described in any one of the preceding three paragraphs, that is further provided, specifically on or in the body portion of the active slender (small diameter) tube or tubular object or instrument, with a bending mechanism. The bending mechanism here is provided in particular adjacent to the active end portion of the slender tube or tubular object or instrument for bending the active end portion thereof as it is embodied, i.e., as an active catheter or guide wire or any other micro electro mechanical system or a system""s active micro-component. The bending mechanism here comprises an elastically deformable outer skeleton that may include an outer elastically deformable tube or tubular member or element as above described, and as a bending actuator that is made of an SMA material.
According to a further alternative form of implementation of the principles of the present invention, there is provided an active slender (small diameter) tube or tubular object or instrument as embodied, e.g., as an active catheter or guide wire or any other micro electro mechanical system or a system""s micro-component that comprises a bending mechanism, a torsionally rotating mechanism, an extending and retracting mechanism, and a stiffness control mechanism, which have an elastically deformable outer skeleton. Alternatively, it may comprise an elastically deformable outer skeleton, a bending mechanism, a torsionally rotating mechanism and a stiffness control mechanism. In specific terms, the elastically deformable outer skeleton may have a portion thereof that may be constituted by an outer elastically deformable tube or tubular member or element that is common to all of the bending, torsionally rotating, extending and retracting, and stiffness control mechanisms, but should preferably have individual portions thereof that are in particular, specific to these separate mechanisms, respectively.
A further specific form of implementation of the principles of the present invention is characterized in that an elastically deformable outer skeleton or skeleton portion specifically provided for the bending mechanism as described above comprises a flat cable or wire type liner coil.
A further specific form of implementation of the principles of the present invention is characterized in that a torsionally rotating mechanism as described above comprises an elastically deformable outer skeleton and torsionally rotating actuator disposed inside of the outer skeleton and secured thereto coaxially therewith. Here, the torsionally rotating actuator is made of a SMA material and upon deformation to have a diameter torsionally varied from the diameter of the SMA made actuator in its natural shape memory state is secured or fastened to the elastically deformable outer skeleton.
A further specific form of implementation of the principles of the present invention is characterized in that a stiffness control mechanism as described above comprises an elastically deformable outer skeleton and a stiffness control actuator disposed inside the elastically deformable outer skeleton and secured thereto coaxially therewith. Here, the stiffness control actuator is made of a SMA material and, as in its natural shape memory state, is secured or fastened to the elastically deformable outer skeleton.
A further specific form of implementation of the principles of the present invention is characterized in that each of a bending mechanism, a torsionally rotating mechanism, an extending and retracing mechanism and a stiffness control mechanism as described above, is provided at each of its opposite ends with electrode connectors.
A further specific form of implementation of the principles of the present invention is characterized in that an elastically deformable outer skeleton as described above, comprises a spiraled board having a plurality of wires incorporated therein with either of a spring structure of plastic made flat wires and a spring structure of insulator coated super-elastic alloy made flat wires.
A further specific form of implementation of the principles of the present invention is characterized in that a SMA made actuator member as described above has a flat cable or wire spring structure.
A further specific form of implementation of the principles of the present invention is characterized in that a flat cable or wire spring structure and SMA made actuator as described above has a heater provided therefor.
Such an active slender tube or tubular object or instrument as described above, when it is used as an active component of a micromachine system such as a catheter, guide wire or any other system""s active micro-component as previously described, is found to be capable of readily bending, torsionally rotating, and/or extending and retracting, and/or adjusting stiffness of, its active portion to a required extent or extents with ease and precision.
An outer skeleton structure combined with a SMA made actuator as described above permits each to be configured in a flat spring structure and thus permits a greater number of thinner wires to be included in each of them.
Also, locating a SMA actuator member that is a heat emitting body inside an outer skeleton structure with enough distance from the surface of the active slender tube or tubular object or instrument can effectively limit the surface temperature up to or well below 41xc2x0 C. that is tolerable for the human body.
In accordance with the principles of the present invention in a second aspect thereof and in another form of implementation thereof, there is also provided a method of making a slender (small diameter) tube or tubular object or instrument that may be embodied, i.e., as an active catheter or guide wire or any other micromachine system or a system""s active micro-component, which method comprises the steps of: preparing an actuator made of a shape memory alloy (SMA) and configured to form a portion of the slender tube or tubular object or instrument; disposing outside of the SMA made actuator and coaxially therewith an elastically deformable outer skeleton configured to form a portion of the slender tube or tubular object or instrument; and fastening the SMA made actuator member and the outer skeleton together.
A certain specific form of implementation of the principles of the present invention in the second aspect thereof is characterized in that the step of disposing described above includes a step of cladding a rod with the SMA made actuator member.
Another specific form of implementation of the principles of the present invention in the second aspect thereof is characterized in that the step of disposing described above includes steps of disposing a rod on the SMA made actuator member and cladding the rod with the outer skeleton.
Yet another specific form of implementation of the principles of the present invention in the second aspect thereof is characterized in that the step of disposing described above includes a step of cladding a pipe shaped jig that is triangular in cross section with the SMA made actuator member.
A further specific form of implementation of the principles of the present invention is characterized in that the step of disposing described above includes a step of electrically connecting a lead wire to the SMA made actuator member.
A further specific form of implementation of the principles of the present invention in the second aspect thereof is characterized in that the step of fastening described above includes a step of bonding the SMA made actuator member and the outer skeleton together with an adhesive.
An alternative specific form of implementation of the principles of the present invention in the second aspect thereof is characterized in that the step of disposing described above includes a step of forming non-insulated portions on the SMA made actuator member and the outer skeleton in their corresponding areas, and the step of fastening described above includes a step of passing an electric current through the SMA made actuator member and the outer skeleton in an electroplating liquid to deposit a metal on the non-insulated portions from the liquid and thereby to electrically join the actuator member and the outer skeleton together at those corresponding areas.
Another alternative specific form of implementation of the principles of the present invention in the second aspect thereof is characterized in that the step of disposing described above includes steps of forming non-insulated portions on the SMA made actuator member and the outer skeleton in their corresponding areas and disposing at least one lead wire adjacent to the non-insulated portions, and the step of fastening described above includes a step of passing an electric current through the lead wire, the SMA made actuator member and the outer skeleton in an electroplating bath to deposit a metal on the lead wire and the non-insulated portions from the liquid and thereby to electrically join the actuator member, the outer skeleton and the lead wire together in those corresponding areas.
Another alternative specific form of implementation of the principles of the present invention in the second aspect thereof is characterized in that the step of disposing described above includes a step of forming non-insulated portions on the SMA made actuator member and the outer skeleton in their corresponding areas, and the step of fastening described above includes a step of passing an electric current through the SMA made actuator member and the outer skeleton in a liquid containing an insulating resin to electro-deposit the insulating resin on the said non-insulated portions from the liquid and thereby to join the actuator member and the outer skeleton together at those corresponding areas.
Another alternative specific form of implementation of the principles of the present invention in the second aspect thereof is characterized in that the step of disposing described above, includes steps of forming a non-insulated portion on the SMA made actuator member and electroplating the non-insulated portion to form an electrically conductive junction thereat, and the step of fastening described above includes a step of passing an electric current through the SMA made actuator member and the outer skeleton in a liquid containing an insulating resin to electro-deposit the insulating resin on the non-insulated portion and throughout, on the outer skeleton from the liquid solution and thereby to join the actuator member and the outer skeleton together.
A further specific form of implementation of the principles of the present invention in the second aspect thereof is characterized by further steps of forming non-insulated portions on the SMA made actuator member and the outer skeleton and passing an electric current through the SMA made actuator member and the outer skeleton in an electroplating bath to deposit a metal on the non-insulated portions from the bath and thereby to electrically join the actuator member and the outer skeleton together.
A further specific form of implementation of the principles of the present invention in the second aspect thereof is characterized by a further step of removing natural oxide layer on the SMA made actuator member and the outer skeleton immediately prior to depositing the metal and/or insulating resin, respectively.
A further specific form of implementation of the principles of the present invention in the second aspect thereof is characterized by a further step of drying by vacuum drying.
A further specific form of implementation of the principles of the present invention in the second aspect thereof is characterized in that, in the step of disposing described above, the SMA made actuator member is disposed so as to be elastically deformable.
The method as described above of making a slender (small diameter) tube or tubular object or instrument is found to permit manufacture of such slender tubes or tubular objects or instruments with increased precision.
Also, if fastening is carried out by electric metal plating or resin deposition, it can be effected at a number of points of connection simultaneously.
These and other features, objects and advantages will be understood and become more readily apparent to those of ordinary skill in the art, from the following detailed description of the preferred embodiments as illustrated in the various drawing figures in the accompanying drawings.